Mixing valves are widely used for household and sanitary purposes for the delivery of cold and hot water flowing from supply pipes. Commonly, these mixing valves include a fixed valve plate of hard material such as ceramic or plastic having openings communicating with two supply pipes, a control mechanism, a slide operably connected to the control mechanism, a guide ring placed above the slide, a space surrounding the slide that communicates with a spout outlet, and a movable valve plate of hard material fixed to the slide having its own openings selectively alignable with the openings of the fixed plate so as to regulate the delivered flow rate and the mixing ratio of the liquids from the two supply pipes. One such valve is shown in U.S. Pat. No. 4,325,403 issued to Uhlmann on April 20, 1982 and is incorporated herein by reference.
In some cases, these mixing valves present the particular problem of being noisy. Noise occurs when the passage of one flowing liquid is very throttled. In such conditions, in fact, the flow, throttled among the sharp edges of the disks of hard material, attains great speed and can produce cavitations by producing vibrations either directly or because of the impact of the flow against some faucet surfaces.
On the other hand, the application of the known preclosing devices makes the construction more complicated and can bring about an excessive reduction of the water flow that the faucet can deliver. In some cases, operation of a faucet is improved by inserting into suitable positions, for example, inside the slide, some metal networks, such as screens. However, these screens have a limited effectiveness, reduce the deliverable water flow, and moreover they suffer from occlusions easily, which further reduce the water flow.
What is needed is a particular structure suitable to reduce the noise of a faucet of the considered type by forming a preclosing unit able to control the flow and to decrease its vibrations when it is highly throttled, without any appreciable influence on the faucet behavior when non-throttled flows are delivered.
A structure is needed that has the above mentioned advantages which can be industrially produced without any appreciable increase of the production costs.
A structure is also needed that, while maintaining the mentioned technical advantages, provide a considerable increase in the maximum water flow of the faucet.